JPS6052941B2 - Method for manufacturing curl-free composite material consisting of polyimide and metal foil - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in the method of manufacturing a composite material consisting of polyimide and metal foil.

Composite materials of polyimide resin and foils of metals such as aluminum, copper, or nickel are used to make things such as speaker diaphragms, flexible printed circuit boards, and planar heating elements.

This composite material has conventionally been manufactured by laminating a polyimide film and a metal foil with an adhesive layer interposed therebetween. However, conventional products have been unsatisfactory in electrical insulation, heat resistance, etching suitability, and adhesive strength between the film and foil. Since the cause is mainly the presence of an adhesive layer, efforts have been made to obtain products that do not use adhesives. One method is to dissolve a polyimide precursor in an organic solvent such as N-methylpyrrolidone or DMF (dimethylformamide) and apply it onto a metal foil, where a ring-closing reaction takes place to form polyimide. At the same time, attempts were made to remove the solvent and obtain composite materials with strong bonds.

Recently, so-called solvent-soluble polyimide resins, which have already been ring-closed to form polyimide but are soluble in solvents, have become commercially available.This solution is applied onto metal foil and heated. By removing the solvent and forming a dry film, it has become possible to easily create composite materials. However, when this manufacturing method is used, the volume of the polyimide resin coating layer generally shrinks violently during the solvent removal and film formation process, and as a result, the composite material tends to have the polyimide layer curled inward, resulting in products that are often unsuitable for practical use. The problem is that it can be done.

This tendency is more pronounced as the polyimide layer becomes thicker. As a measure to avoid this problem, the thickness of the polyimide layer is reduced to 5 μm.
It was proposed to control the thickness within ±10% (Japanese Patent Laid-Open No. 54-38383).
issue).

If the thickness of the polyimide layer is limited to 5μ or less,
Since this composite material can only be used in some of the applications, the present inventor investigated a method to obtain a composite material with a thick polyimide layer without curling, and as a result, the heat treatment after manufacturing The inventors have discovered that this is effective, leading to the present invention.

The method of manufacturing a curl-free composite material made of polyimide and metal foil according to the present invention includes a step of forming a polyimide resin film on the metal foil to obtain a composite material, and then applying the polyimide resin film to the composite material. It is characterized by adding a heat treatment step in which it is held at a temperature above the glass transition point and below the thermal decomposition point for a certain period of time. Formation of the polyimide resin film on the metal foil may be carried out by applying a polyimide precursor solution and ring-closing according to the conventional technique, but application of the above-mentioned solvent-soluble polyimide resin solution is more effective. It's convenient.

In either case, sufficient strength can be obtained without adhesive.
For polyimide resins that are easily available on the market, the heat treatment temperature is 270°C or higher, preferably 310 to 40°C.
Select from a range up to 0°C.

The higher the temperature, the shorter the time required for a sufficient heat treatment effect to appear, ranging from 3 to 2 minutes to several minutes, but at low temperatures it may take from 2 to 3 hours to nearly 5 hours. The heating means is arbitrary, such as an electric furnace, hot air blowing, and infrared single-ray irradiation. It has been found that the heat treatment is more effective and the heating holding time can be shortened if it is performed while applying tension to the composite material, especially the polyimide resin layer.

This effect is 200v/C! This is noticeable when a tension of about n or more is applied. When carrying out the present invention, the formation of the resin film and the heat treatment are performed continuously in-line, and the heating is performed at a relatively high temperature and under tension so that the effect can be obtained in a short period of time. can be completed in an integrated process, which can be recommended as a highly productive method. Of course, once the composite material is made and rolled up, (
In some embodiments, the roll is held in a furnace and heat treated (winding with the polyimide layer on the outside is preferred for the reasons stated above). In other words, the method of the present invention can also be called a method for removing curls from a composite material produced with curls. According to the method of the present invention, curl-free products can be produced in composite materials of any thickness combination of both polyimide and metal foil.

Claims (1)

[Claims] 1. Following the step of obtaining a composite material in which a polyimide resin coating is formed on a metal foil, the coating material is heated to a temperature above the glass transition point and below the thermal decomposition point of the polyimide resin. A method for producing a curl-free composite material made of polyimide and metal foil, which is characterized by adding a heat treatment process to maintain the properties. 2. The composite material according to claim 1, wherein the polyimide resin film is formed on the metal foil by applying a solvent-soluble polyimide resin solution and heating to remove the solvent. manufacturing method. 3 Heat treatment at 270°C or higher, preferably 310 to 40°C
A method for producing a composite material according to claim 1, which is carried out for 30 seconds to 5 hours at a temperature of up to 0°C. 4. The method for producing a composite material according to claim 1, wherein the heat treatment is performed while applying tension to the composite material.